Vacuum-tube rectifier



Feb. 18, 1930. AKERS 1,747,852

VACUUM TUBE RECTIFIER Filed April 15, 1921 /-77/ Eye CZ Sinwf b 3 L2 sin (of Patented Feb. 18, 1930 UNITED STATES MILTON K. .AKERS, OF TROY,

PATENT OFFICE OHIO, ASSIGNOR TO WESTERN ELECTRIC COHPANY, IN-

CORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK VACUUM-TUBE RECTIFIER Application filed April 15, 1921.

This invention relates to a rectifier, and more particularly to a three-electrode electric discharge rectifier.

One of the objects of the invention is to produce by means of rectification, a flattopped or substantially uniform continuous current wave.

Further objects of the invention will be readily suggested by a reading of the detailed disclosure which follows.

In this specification the terms vacuum tube and electron discharge device will be used to describe generically not only evacuated devices of the three-element type such as the gas-tube of Von Lieben and the pure electron discharge tube, but also the mercury vapor rectifier.

According to the invention, the rectifier comprises, in general, a three-electrode electric discharge device in series with a load and a source of alternating E. M. F. to be rectified. The impedance of the series circuit comprised by the anode-cathode space path in the electric discharge device is varied in consonance with the instantaneous values of the alternating E. M. F. This function is accomplished by impressing on the control electrode a constant positive E. M. F., on which is superposed an alternating E. M. F. of the same frequency as that in the series circuit, and displaced 180 electrical degrees there- By employing a plurality of electric discharge rectifying devices, both alternations may be rectified according to a method familiar in the usual mercury vapor rectifying system. The addition of the constant potential impressed on the control electrode results in a condition wherein the rectified current varies from a maximum to a minimum value without passing through a zero value.

This rectifier produces a rectified current wave comparable in smoothness and regularity with that heretofore obtained, for example, by the use of a polyphase source with Serial No. 461,685.

series impedance in the load circuit, but without the use of said impedance.

he invention will be more fully understood by a reading of the detailed description which follows, ta en in connection with the annexed drawings, which illustrate a specific embodiment of the invention, and in which Fig. 1 illustrates graphically the electrical relations in a common form of two-element tube. Fig. 2 correspondingly illustrates the electrical relations 111 a three-element tube, used in accordance with the present invention. Fig. 3 shows a simple circuit arrangement for carrying out the principles of the invention. Fig. 4 shows an arrangement by means of which both halves of the alternating voltage Wave may be utilized. Fig. 5 shows the use of the system of Fig. 4 with a polyphase current source, and Fig. 6 illustrates the electrical relations in a system of the last-mentioned type.

f a sinusoidal electromotive force E sin I =f(E Slll wt B),

in which 1;, is the current which is supplied by the rectifier to the load, the particular function being substantially proportional to the square of the quantity in brackets.

Fig. 1 shows the relations expressed by this equation, the abscissa; being values of the independent variable t, the two series of curves indicating the results obtained by use of two tubes to utilize both halves of the voltage wave in a manner common to the art of mercury vapor rectifiers, and which will be hereinafter explained with reference to Fig. 4 of the drawings. The current curve 1,, has been drawn to show the squared characteristic, which, however, is made less pronounced than it would otherwise be by reason of the effect of the variable term B which has a maximum eflect at the peak of the curve. It is apparent from this figure that the rectified current wave is more pointed than the impressed voltage wave, and, therefore, that curve is proportional to of zero current. The inductance of the trans-' former, by means of which alternating voltage is im ressed on the rectifier, contributes to this e ect and by adding sufiicient inductance in series therewith, or to the common rectified current circuit if two rectifier units are associated with a three-terminal transformer, the rectified current may be caused to be continuous and substantially uniform.

Since the area beneath the rectified current the product of time go and the square of the electromotive force the curves are referable to an energy basis and accordingly it will be evident from a consideration of the area between consecutive lobes of the rectified current curve that a reactive .5 element or elements of considerable energy tube, the equation will be storage capacity is or are necessary in order to cause the rectified current to be substantially uniform.

Deriving the relations for a three-element changed by the addition of terms ex ressing the effect of the contribution of the control element to the field. The equation is accordingly as follows:

lb=f(Eb sin mt-B:*:K E si M1330) The subscripts in which K C represents the contribution to the field on account of the steady value of potential impressed on the control element and K 12 sin at the corresponding contribution of the variable component, the coefficient K being the voltage amplification constant. b and c are chosen in deference to the conventional nomenclature in which the source of space and grid voltages are respectively denominated b and 0 batteries. The variable potential E sin wt is impresse on the impedance control element by means of a circuit suitably connected to the alternating current source. In the ractical operation of the system, the term i2 1), sin wt is'derived from a voltage displaced in phase a hundred and eighty electrical degrees from the voltage E sin wt and the otential C is given a positive value. Accordingly the equation may be expressed as follows:

This equation, as well as the corresponding equation for the two-element tube, is applicable during the intervals when the potential of the plate, both by reason of directly aplied electromotive forces and by reason oY the resultant of all the electromotive forces,

is positive, i. e. when E, sin mt is positive and :t the same time the bracketed term is posi- Fig. 2 shows approximately the form of the current wave resulting from the above described mode of eration, certain voltage waves also being 'siown. The curves are plotted for two tubes .related to each other in a manner similar to the case of Fig. 1, those related to one of the tubes being identified by descriptive labels. The broken line curves represent the potentials K F sin wt+K C, and indicate the potentials impressed on the control elements as referred to the late electrodes by means of the multiplier Only so much of the broken line curves as is here applicable is shown. As is apparent from the equation before-mentioned, the current 1,, is a function of the eometric sum of the full and broken curves.

he shape ofthe resultant curve is, of course, affected by the term B of the above equation, similarly as in Fig. 1, although to a considerably "ss extent since this quantity is itself a function of the current L, which, on account of other factors, strongly tends to be uniform in amplitude. Further, from a consideration of the two conditions that must be satisfied, it is evident that current will flow only during the interval of time when E, sin wt is positive and will accordingly drop to zero at the instants when this quantity decreases from a finite positive to a zero value. The current resulting from a single tube ma accordingly be represented by the curve Or NP, the shape of the portion MN depending on the particular function of the bracketed term of the equation, as in the case of the current curve of Fig. 1. It should be noted that the effect of the constant potential applied to the control element is to adjust the position of the broken line curve in such manner as to increase the ordinates of the resultant current curve, the increase being relatively greater at the ends of the variable portion than at the maximum amplitude point. Further, the effect of the component of electromotive force E sin out impressed on the control electrode, is to variably decrease the ordinates of the curve that would otherwise result. The summation effect is a sensible flattening of the current curve as compared with the corresponding curve in Fig. 1. The use of a single tube will result in a wave of the form described for each positive alternation of the voltage E sin wt. The use of a second tube will result in a similarly shaped wave PNQS. The conjoint use of two tubes will accordingly give a substantially constant curve of the form In practical operation, by reason of the inductance of the circuits associated with the tubes, the current will not tend to decrease abruptly from and Q, for example, to

zero, but the form of the wave will be substantially as shown in heavy lines, the resultant effect being made evident in a somewhat smoother current curve than that shown.

Fig. 3 shows a simple system for carrying out the purpose of the invention, a single tube being used and B indicating the load. The battery 3 impresses a constant positive potential on the grid, the resistance 1' being included in circuit to avoid excessive energy loss when the grid is positive, so far as is consistent with the use of a proper grid potential. Included in the grid circuit is a winding 2 of transformer T. As shown, this winding is so arranged with relation to the grid and to winding 1 of the transformer that the plate and grid are of opposite polarity.

An alternating E. M. F. impressed upon the primary winding of transformer T is reproduced in the secondary circuit, which includes in series the secondary winding 1, the load B and the space path between the cathode and anode of the uni-directionally conducting electric discharge rectifying device B. An alternating E. M. F. is also reproduced in the secondary winding 2, and is superposed on the constant positive E, M. F. from battery 3. The superposed alternating E. M. F. is displaced 180 electrical degrees from the alternating E. M. F. impressed between the cathode and anode of the rectifying device R, and

varies in accordance with the instantaneous values thereof. This super osed alternating E. M. F, being impresse upon the control electrode or grid of the rectifying device R. varies the impedance of the cathode-anode space path in consonance with the instantaneous values of the E. M. F. impressed between the cathode and anode, and consequently influences the magnitude of the rectified current wave.

A circuit arrangement as above described will rectify every alternate half cycle of impressed E M. F., the portion of Fig. 2 at the left showing the electrical conditions in the tube during one-half c cle.

By means of the circuit arrangement of Fig. 4, bothhalves of the impressed voltage wave may be rectified. The arrangement, as affecting each tube separately, is identically the same as that of Fig. 3, the use of the two tubes making possible an eflicient use of the transformer secondary winding inasmuch as that portion of the winding utilized to impress positive potential on the grid of one tube during one half cycle, impresses positive potential on the plate of the other tube during the other half cycle. By the use of the two tubes arranged as here shown, a continuous rectified current of the form shown in Fig. 2 results.

i Fig. 5 shows an adaptation of the invention to use with a two-phase, star-connected system, the connection of each pair of tubes rent wave in Fig. 2 and may be considered as derived from devices R and R, in identically the same manner as curve L, of the latter was derived from the circuits illustrated in Fig. 4. The current I may be similarly derived from devices R and R the maximum points of the two curves being displaced from each other by an interval of ninety electrical degrees in accordance with the phase relations of the voltages in a two-phase system. The current in load circuit B is the resultant of these two currents and, as will be apparent, is more constant than either of its component currents, I and I It is, of course, obvious that the invention is not confined to use with the single and twophase systems shown, but that any single phase or polyphase system whatever can e used by a simple and obvious extension of the principle here illustrated.

What is claimed is: I

1. In a rec-titfying system, in combination, an electric discharge device, said device including three electrodes, an alternating voltage source connected to two of said electrodes, means for impressing a variable voltage on the third electrode, and further means for simultaneously and constantly impressing-a positive E. M. F. on the third electrode.

2. In a rectifying system, in combination,

an electric discharge device, including a cathode, an anode and a control electrode, an alternating voltage source included in circuit with the cathode and the anode of said discharge device, a control element included in said discharge device, means for impressing on said control element a variable potential substantially opposite in phase to the potential impressed on the anode of said discharge device, and means in circuit with said means a for impressin a constant positive E. M. F. on said control e ement.

3. A rectifying system comprising, in combination, an electric discharge device, said electric discharge device including an electron emitting cathode, an anode and a control element, an alternating voltage source connected to the said cathode and anode, circuit means connecting said control element to a point in the alternating voltage source displaced in phase substantially 180 electrical degrees from the oint of connection of said anode, and an ad 'tional means'included in the last mentioned circuit for impressing a constant positive E. M. F. on said control element.

4. A rectifying system comprising, in combination, a three-electrode vacuum tube, said tube including an electron emitting filament, a plate, and an impedance controlling element, an alternating voltage source connected to said filament and plate, means for impressing on said impedance controlling electrode a variable potential substantially opposite in phase to the potential impressed on said plate, and an additional means for impressing constant positive E. M. F. on the said impedance controlling element.

5. In a rectifying system, in combination, a three-electrode discharge device comprising an anode, a cathode and an impedance controlling element, means for impressing an alternating difference of potential between said cathode and anode, means for impressing between said cathode and impedance controlling element an alternating difference of potential in such a manner that the potential of the element is always displaced 180 electrical degrees from the potential of said plate and means for impressing a constant positive E. M. F. on said element.

6. In a rectifying system, in combination, a three-element discharge device, comprising an anode, a cathode and an impedance controlling element, an alternating voltage source in circuit with said anode and cathode, an energy absorbing means being also contained in said circuit, means for impressing between said cathode and said impedance controlling element a difference of potential substantially opposite in phase to the difference of potential impressed between the cathode and anode, and an additional means in circuit with said last mentioned means for impressing on said element a constant positive E. M. F.

7. In a rectifying system, in combination, two three-element discharge devices, each of which comprises an anode, a cathode and an impedance controlling element, an alternating current windin means connecting the' ends of the said winding to the respective anodes of said electric discharge devices, a load circuit connecting the cathodes of said devices in common with substantially themiddle point of said winding, means connecting each of said imped'ancecontrolling elements to the said winding at a point in that half of the winding other than that to which the corresponding anode is connected, the connections of the two controlling elements being symmetrically s aced from said middle point, and a source 0 constant E. M. F. in-

cluded in the circuit of each said impedance controlling element, the connections of said controlling elements being adjusted, so that the corresponding otentlals as measured at the anodes are less t an the potentials direct- 1y applied to the anodes by said winding and said source being so connected that the impedance controlllng element is given a constant positive otential.

8. A metho of producing a rectified current of substantially uniform wave form and.

supplying it to a load circuit involving the use 0 a three-element electric discharge device having a cathode, an anode and a control element, an alternating voltage source and a load circuit being serially connected to said anode and cathode, which consists in impressing on the control element, a variable potential having the same wave form as the alternating current to be rectified and opposite thereto in phase, and in simultaneously impressing on the third electrode a constant positive E. M. F. I V

9. In a rectifying system, the combination of an electric discharge device having a cathode,\an anode and a control electrode, a load, a source of alternating voltage connected in series with the load and the cathode anode space path of the electric discharge t e 

